In the present work, three different porous supports, i.e. MCM-41, SBA-15 and UVM-7 were synthesized and functionalized with three different aminosilanes (C₉H₂₃NO₃Si, C₈H₂₂N₂O₃Si and C₁₀H₂₇N₃O₃Si). All the synthesized samples were characterized using XRD, nitrogen physisorption, elemental analysis and acid–base titration, SEM and TEM. The obtained results revealed that all the samples have a well-ordered structure and amine groups were successfully grafted on their pore surfaces. Then, the ability of amine-functionalized samples to adsorb H₂S was investigated. In the case of MCM-41, changing the aminosilane functional group did not change t_bp (the time at which the outlet concentration of H₂S reaches its maximum admissible value in the effluent). SBA-15 functionalized with C₈H₂₂N₂O₃Si showed enhanced t_bp in comparison with C₉H₂₃NO₃Si, but C₁₀H₂₇N₃O₃Si showed very low t_bp (even lower than C₉H₂₃NO₃Si) which might be attributed to pore blocking originating from the very large size of C₁₀H₂₇N₃O₃Si. UVM-7 had the highest t_bp for all three of the aminosilane functional groups. This might be attributed to the very large pore size of UVM-7 with respect to those of SBA-15 and MCM-41. In addition, nanosize particles of UVM-7 facilitate the adsorption of H₂S for this type of adsorbent, which should be due to the unconstrained diffusion of H₂S within the mesopores of UVM-7. The efficiency of an aminosilane functional group strongly depends on the pore size of the support rather than its surface area.